UTfan01SS

iTrader: (1)

I've got a 99 model LS1 that was completely gone through and freshened up over the winter. Bored to a 3.905 bore, new pistons and rings, 799 heads and a Comp LSR cam. Motor runs good but has a miss when revving up to 2000 RPM. It pops through the exhaust and misses, but if I rev it up the miss will go away. Only does this if you hold the throttle at a certain RPM.

Fuel pressure is at 58 psi at the rail.
Ignition advance is around 25 degrees at idle. All cylinders have consistent temps at the header flange. Runs a little rich but both O2 sensors are working and within range. Not sure if I have a bad injector or something. Plugs and wires are brand new also... new MAF and new O2 sensors. Kinds baffled as to what is causing this.

Completed a compression test today after warming the engine up. Pulled all 8 plugs and held the throttle blade wide open. All cylinders except for two were at 180psi. Cylinder number 3 and 4 were at 165psi.. that seems acceptable for a new motor but wanted to get some opinions. Haven't driven the car yet as I'm finishing up the suspension. So its still not 100% broken in....

And ideas on the miss?

Brando5641

iTrader: (3)

Has it been tuned?

farmington

iTrader: (14)

showing any codes?

64post

iTrader: (5)

If you could access a scan tool, go to engine data/misfire data and isolate the cyl(s) that are missing then you could get a better idea as well as switching coils etc.. and know where to spend your time.

UTfan01SS

iTrader: (1)

It had a start up tune put on it, seems a little rich but it runs good. Finds its idle really quick and runs fine. Other than that slight miss. Doesn't throw any codes and all eight plugs look consistent. Is there a way to do an Ohm check on the fuel injectors to see if I have a bad one?

UTfan01SS

iTrader: (1)

It had an O2 code when I first started it, so I replaced both O2 sensors with new ones and the codes went away. It has me baffled... definitely don't think its anything internal.